1. Field of the Invention
The present invention relates to a cold gas generator for inflating a gas bag (airbag).
2. Description of Related Art
Such gas generators are used for inflating a gas bag with stored gas in the case of activation, e.g. an airbag in a car.
A problem encountered in the filling of airbags is the high temperature development which occurs especially in pyrotechnically generated gas, which in addition to the endangerment of the passengers, can also lead to the thermal destruction of the gas bag.
It is known with respect to hybrid gas generators which comprise both a pyrotechnic propellant charge as well as a cold gas source in the form of a gas storage means that the hot gas stream of a pyrotechnic propellant charge burns through a sealing element closing off the gas container. Such a propellant charge is usually ignited by a primer (an igniter provided with a jacket which contains in its interior a small quantity of a pyrotechnic priming charge which can be ignited via ignition pins which are guided into the propellant charge and to which an electric voltage is applied), which primer, with a charge of approximately 100 mg of pyroteclhnical material, has no significant influence on the output of the gas generator. Such a hybrid gas generator is disclosed in EP 699.231 A1 for example.
Cold gas generators are also known which omit the use of an additional propellant gas charge and exclusively use a primer for destroying the sealing element. This leads to the advantage that by omitting the additional propellant charge the temperature of the gas in the gas bag is reduced to the thermodynamic behavior of the employed gas in the gas pressure vessel, as a result of which the same is thus present in a virtually cold condition. Moreover, the production of poisonous residual matter is further prevented which originate from the burn-up of additional pyrotechnic propellant charges. Such a cold gas generator is disclosed in DE 100 38 673 A1 for example. The stream of hot gas as produced by the primer is guided in a small, enclosed space directly onto the sealing element, which is a membrane. As a result of the ignition of the primer in an enclosed space, a blast wave or shockwave is produced which destroys the sealing element. In order to produce this small enclosed room whose one side is delimited by the sealing element, high requirements are placed on the tubular support by the contact with the pressurized sealing element, leading to an unnecessary complex production. Moreover, the annular discharge cross section which is complex with respect to its flow dynamics and which is to be produced after the destruction of the sealing element causes insecurity with respect to the reproducibility of the opening behavior. A further disadvantage is that the filling and thus also the checking of the gas pressure vessel can only occur after the complete assembly of the cold gas generator because the sealing element would not withstand the interior pressure of the gas pressure vessel without additional support.